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# If x^4 = 16 and y^2 = 36, then the maximum possible value of x - y is

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Joined: 02 Sep 2009
Posts: 58417
If x^4 = 16 and y^2 = 36, then the maximum possible value of x - y is  [#permalink]

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01 Mar 2018, 22:57
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Difficulty:

15% (low)

Question Stats:

84% (00:44) correct 16% (00:36) wrong based on 71 sessions

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If x^4 = 16 and y^2 = 36, then the maximum possible value of x - y is

(A) -20
(B) -4
(C) 6
(D) 8
(E) 20

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Re: If x^4 = 16 and y^2 = 36, then the maximum possible value of x - y is  [#permalink]

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01 Mar 2018, 23:31
1
Bunuel wrote:
If x^4 = 16 and y^2 = 36, then the maximum possible value of x - y is

(A) -20
(B) -4
(C) 6
(D) 8
(E) 20

The maximum value is possible when we use the biggest value of x and lowest value of y.

In this case, if $$x^4 = 16$$, x could take the value of +2 or -2
Similarly, if $$y^2 = 36$$, y could take the value of +6 or -6

Therefore, the maximum possible value of x-y is $$+2 - (-6) = 2 + 6 = 8$$(Option D)
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Re: If x^4 = 16 and y^2 = 36, then the maximum possible value of x - y is  [#permalink]

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01 Mar 2018, 23:37
$$x{4}=16$$ , so x can be +2 or -2.
$$y{2}=36$$ , y can be +6 or -6.

Maximum value of x-y is 2-(-6) = 8

Ans: D
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Re: If x^4 = 16 and y^2 = 36, then the maximum possible value of x - y is   [#permalink] 01 Mar 2018, 23:37
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